With the development of science and technology, fuel vehicles are being replaced by environment friendly and energy saving electric vehicles. However, the popularity of the electric vehicles encounters some problems, among which high driving mileage and fast charging technology has become major problems in the promotion of electric vehicles.
Currently, large-capacity batteries are used in most electric vehicles. However, although these batteries may enhance a battery life of the electric vehicle, they make a charging time too long. Although a specialized DC (direct current) charging station may charge a battery quickly, problems such as high cost and large occupied area make the popularity of such an infrastructure encounter a certain difficulty. Moreover, because of a limited space of the vehicle, an in-vehicle charger may not satisfy the requirement of a charging power due to the limitation of its volume.
A charging solution currently used in the market includes the following solutions.
Solution (1)
As shown in FIGS. 1-2, an in-vehicle charging-discharging device in this solution mainly includes a three-phase power transformer 1′, a three-phase bridge circuit 2′ consisting of six thyristor elements, a constant-voltage control device AUR, and a constant-current control device ACR. However, this solution causes a serious waste of space and cost.
Solution (2)
As shown in FIG. 3, an in-vehicle charging-discharging device in this solution includes two charging sockets 15′, 16′ to adapt to the single-phase/three-phase charging, which increases the cost. A motor driving loop includes a filtering module consisting of an inductor L1′ and a capacitor C1′. When a motor is driven, a loss of a three-phase current is generated when it flows through the filtering module, which causes a waste of an electric quantity of a battery. With this solution, during the charging-discharging operation, an inverter 13′ rectifies/inverts an AC (alternating current), and the voltage after the rectifying/inverting may not be adjusted, such that a battery operation voltage range is narrow.
Therefore, most AC charging technologies currently used in the market are a single-phase charging technology, which has disadvantages of low charging power, long charging time, large hardware volume, single function, restriction by voltage levels of different regional grids, etc.
As key components of the electric vehicle, a motor drive system and a charging system of the power battery have a rapid technology progress. The motor drive system in the conventional electric vehicle acts as an independent system and has independent power conversion module and control module, as long as it ensures the motor drive requirement and a part of the vehicle requirements when the vehicle is running. The charging system of the power battery generally includes an in-vehicle AC charging system and a rapid DC charging system. The in-vehicle AC charging system has the power conversion module and the control module, and can charge the power battery with a small power. The rapid DC charging system only requires a corresponding distribution circuit and a battery management system at the vehicle side to perform an auxiliary control, but the charging apparatus needs large devices such as the power conversion module. For the electric vehicle provided with power battery having relatively larger power, in order to ensure the convenience and rapidness of the charging, both of these two charging systems are needed to provide. Currently, with the development of technology and the urgent requirement of reducing cost, the motor drive system, the charging system, and even the inverter system configured to discharge externally are developed towards integration and unification gradually. The integration includes the integral formation of the common control module and the power modifying module.
However, since this integrated system has many functions, a complexity of the system is increased greatly, and its cooperation with other systems in the vehicle faces severe challenges. In addition, accompanying problems such as mutual interference, a function switching safety and a heat dissipation requirement may occur. Thus, conventional independent processing mode cannot satisfy the requirements.